In general, a piston including a piston main body made of aluminum or an aluminum alloy and a method for manufacturing the same are known. Such a piston and a method for manufacturing the same are disclosed in Japanese Patent Laying-Open No. 2008-51091, for example.
In Japanese Patent Laying-Open No. 2008-51091, there is disclosed an internal combustion piston on which shot peening treatment is performed by injecting injection powders of strengthening elements and/or photocatalytic elements onto a surface of a piston main body made of an aluminum-silicon alloy. On this internal combustion piston, the shot peening treatment is performed, whereby the aluminum-silicon alloy in the vicinity of the surface of the piston main body is modified, and the strength is improved to some extent.
In recent years, a reduction in the weight of the piston is significantly required, and hence an additional reduction in the thickness of the piston is required. Even if the thickness of the piston is further reduced, it is necessary to ensure fatigue strength in a high-temperature environment required by the piston.